The primary objective of this proposal is to determine the mechanism(s) of adenosine regulation of adenylate cyclase from cultured human cells (the 132-lNl astrocytoma cell, the WI-38 lung fibroblast, and the transformed WI-38 line, VA13). To these ends we will continue our studies of the mechanism of: (1) adenosine stimulation of adenylate cyclase; (2) Methylxanthine inhibition of this stimulation; (3) adenosine induced desensitization; and (4) the adenosine inhibition of adenylate cyclase. We will characterize the effects of adenosine and methylxanthine derivatives in search of analogues most suitable for labelling, defining and isolating adenosine (and/or methylxanthine) receptors and the inhibitory adenosine site. To aid in all of our work we will continue our characterization of detergent effects on and solubilization of the components of the adenylate cyclase complex. We must define the components of the adenylate cyclase complex to understand their interactions; e.g., the receptors, GTP-dependent coupling protein(s), catalytic protein(s) and the membrane lipids and proteins. In addition, we will continue our studies of hormone (epinephrine and prostaglandin) desensitization of the WI-38 adenylate cyclase which will also include identification of changes in receptor or guanyl nucleotide regulatory proteins.